I run in a class with requires 70CC heads, holly 500 two barrel carb, cast iron exhaust and intake manifold. I am also limited to .390" .410" lift. The motor will not turn more than 6100 rpm. I change the gear from a 3.73 to a 3.90 at the begining of the season and it still turns the same. The valve springs are all within spec, the lifter are anitpump up. It has a good coil and hei module. Am I at the max flow of the factory cast iron gm duel plane intake? I have been wanting to try more timing but have read many horror stories about hyper pistons not holding up. What should I try?
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